Controlled synthesis of hierarchically porous β-Ni(OH)2 microspheres and NiO nanoparticles with the optical property of NiO nanoparticles

In this study, we demonstrate the preparation of novel hierarchically porous β-Ni(OH)2 microspheres constructed with nanoflakes through a simple solution-phase approach, using NiCl2·6H2O and hexamethylenetetramine (HMTA) as the starting materials without adding any additives. NiO nanoparticles with the average diameter of 10 nm were obtained by calcining the as-prepared β-Ni(OH)2 microspheres at 500 °C under ambient pressure. On the other hand, β-Ni(OH)2 nanoplates were prepared by substituting HMTA with NaOH as the basic source, revealing the realization of shape-controlled synthesis of β-Ni(OH)2 nanostructures. Optical property of the NiO nanoparticles was conducted by means of UV–vis spectrum, exhibiting small blue shift compared with the bulk counterpart. The possible mechanisms for selective formation of β-Ni(OH)2 microspheres and nanoplates were in brief discussed.